1. Field of Invention
This invention relates to lubrication for rotating disk information storage devices. More particularly to an apparatus and method for renewing spent lubrication films on rotating disk memories.
2. Background of the Invention
The problem of friction and wear in rotating magnetic disk memories has been approached from two general directions. One was the introduction of flying heads to separate the head from the rapidly rotating disk in an attempt to avoid the problem altogether. The conflicting need to reduce the head/disk separation in quest of higher recording densities causes occasional head disk contact. This problem has been addressed by the use of lubricants. The problem becomes more severe as that head/disk separation continues to be reduced with each successive generation of higher density disk drives. It will become critical when the separation is reduced to zero, as in the case of the scheme called contact recording, where the head slides on the disk surface.
There have been a number of approaches to this lubrication problem. The liquid lubricants used in gamma ferric oxide overcoated disks have been applied to the subsequent generation of metallic thin film media, with limited success. Spin off and evaporation of this liquid layer eventually reduces the efficacy of the lubricant. One approach to this problem, which is taught in U.S. Pat. No. 4,188,434 to Loran, is to mix a solid lubricant with the liquid lubricant.
Another solution is offered in U.S. Pat. No. 4,626,941 to Sawada where the evaporation of the lubricant from the disk surface is suppressed by evaporating quantities of the lubricant from a reservoir placed in the disk drive. This scheme supplies lubricant vapor at a vapor pressure higher than that exhibited at the disk surface via a temperature differential, thus distilling the lubricant onto the operating disk. This method transfers lubricant not only to the disk but also to the other components within the disk drive, and does not regulate how much is transferred to the disk.
As can be seen, the prior art is directed at solving the lubrication problems of flying heads and does so only in an imperfect way. None of the schemes are adequate for the ultimate case of contact recording.
These difficulties can be overcome by abandoning the techniques of trying to suppress the loss of a topical lubricant and resorting to a method of generating the lubricant on the disk surface as it is needed, i.e. adopting a scheme of "lubricant on demand."
Therefore it is an object of this invention to utilize a material, and process of its generation, known as frictional polymer, to solve the problems of lubricant retention in disk drive systems.
The term frictional polymer was coined by Hermance and Egan in the article "Organic Deposits on Precious Metal Contacts" in The Bell System Technical Journal; May 1958 pg 739. This material is a result of catalytic materials rubbing together in low concentrations of organic vapors. As stated there the mechanism is, ". . . first to involve chemisorption of the vapor on the metal, followed by frictional activation and polymerization of the chemisorbed layers to form the visible accumulation." In the case of relay contacts this effect is a nuisance causing open circuits. In the era before heads flew over the disk, and particularly with rhodium overcoated disks, the accumulation was a problem causing head crashes.
This heretofore detrimental effect can be put to use for lubricating disks by limiting the area of catalytic surface relative to the total frictional surface, thus controlling the amount of polymer generated. This is different from the approach of Sawada who teaches the transfer of lubricant from a reservoir to the disk surface. This present invention invokes monomers or mixtures of monomers, that by themselves are not necessarily lubricants, but when transferred to a catalytic surface are polymerized to larger lubricating molecules by the action of friction. This polymerized to lubricant is then spread on the disk by action of the slider. This latter action is related to the self limiting feature of the process. When there is sufficient lubricant polymer on the disk surface, there is also enough to coat the catalyst surface which blocks vapor adsorption, thus controlling the generation of the lubricant polymer.